Production Guidelines from Fides Oro Royal D. Heins Typical dahlia production issues Dahlia production Dahlia production is complicated due to the photoperiodic response of the plant Under Short Days, plants quickly set flowers, form tubers, and grow very compact. Under Long Days, plants can grow vegetatively for extended periods so that flowering is delayed and plants are large. 9-hr 10-hr 12-hr 14-hr 16-hr 24-hr NI Plants are shorter and smaller under short days because plants are forming tubers. 9-hr 10-hr 12-hr 14-hr 16-hr 24-hr NI Dahlia production Proper flowering of dahlia requires proper management during 4 periods of production Stock production Propagation Finish growing prior to transplant week 13 Finish growing transplant wk 18 or later Dahlia production Proper flowering of dahlia requires proper management during 4 periods of production Stock production Propagation Propagation - Photoperiod Propagate plants and then bulk plugs under long days. Long days can be delivered by: 4-hr night interruption day extension lighting to deliver a 16-hr day length Temperature Air temperature is necessary to achieve a media temp of 73 F to 75 F Keys to successful dahlia production Propagate under long days Prior to week 13, provide long days by night interruption lighting just like with mums After week 13, normal days are adequate although long days can continue Dahlia production Proper flowering of dahlia requires proper management during 4 periods of production Stock production Propagation Finish growing prior to transplant week 13 Finish - Photoperiod After transplanting grow under a day extension photoperiod to 14 hours before week 14 to prevent premature budding and flowering. As daylength changes throughout the spring, only extending the day creates challenges to maintain the same 14-hr daylength. Better is to light before sunrise and again after sunset. For example, lights on at 6 am until 8 am and again 5 pm to 8 pm. Dahlia production Proper flowering of dahlia requires proper management during 4 periods of production Stock production Propagation Finish growing prior to transplant week 13 Finish growing transplant wk 18 or later 9-hr 10-hr 12-hr 14-hr 16-hr 24-hr NI Plants are shorter and smaller under short days because plants are forming tubers. 9-hr 10-hr 12-hr 14-hr 16-hr 24-hr NI Keys to successful dahlia production Propagate under long days Flower under intermediate days When transplanted week 18 or later, provide 10 to 14 short days (12-hr night or longer) to plants in the plug, or alternatively, just after transplant Calibrachoa shoot growth without branching when vegetative branching when reproductive To minimize differences in Lindura early- season flowering, provide long days from stick through week 12 for Lindura White and Lindura Yellow